Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 240553
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
153 AM EDT Tue Oct 24 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 328 PM EDT Mon Oct 23 2017

Low pressure moving north across Lower Michigan will continue to
bring heavy rain with some flooding expected through Tuesday. The
low will deepen on Tuesday and winds will be ramping up with some
strong wind gusts Tuesday and Tuesday night.

&&

.UPDATE...
Issued at 957 PM EDT Mon Oct 23 2017

With the potential for Gales less than 12 hrs away we upgraded the
watch to a warning.  No other changes were made to the forecast.

Satellite imagery shows the coldest cloud tops pivoting north of
the region. Radar and rain gage trends show the precipitation is
weakening in intensity. There is still a lot of forcing around
and a very moist airmass in place. Thus it appears mostly light
rain with periods of moderate rain can be expected right into
Tuesday.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 328 PM EDT Mon Oct 23 2017

Heavy rain tonight into Tuesday and high winds Tuesday into
Tuesday night are the main forecast issues in the near term.

The Flood Watch was replaced with areal Flood Warning across the
western third of the forecast area and an areal Flood Advisory to
its east. The southeast zones are not expected to see flooding and
the watch was dropped there.

Surface low was centered just south of AZO at 330 PM and is moving
north with strong area of f-gen expected to continue producing
inch an hour rain rates across the warning area through the
evening. We have been fortunate that the bulk of the heaviest rain
has remained over Lake Michigan so far today, but amounts over 2
inches have occurred across parts of Ottawa, Muskegon, Oceana
Counties with a report of nearly 2.25 inches near Holland at 320
PM. The heavier rain is moving onshore and the HRRR has the f-gen
area pivoting across our northwest zones tonight.

So 3 to 5 inches of rain is possible in the warning area with
amounts of an inch or less across the southeast zones by Tuesday
afternoon.

The other issue we will have to deal with high winds on Tuesday as
the low rapidly deepens across northern Lower Michigan.
Tightening pressure gradient and strong cold advection will
combine to bring gusts to wind advisory criteria during the
morning across the northern coastal zones and by afternoon across
central and southern zones. We have issued a wind advisory for
this area. The winds will subside after midnight as the low pulls
away.

.LONG TERM...(Thursday through Monday)
Issued at 328 PM EDT Mon Oct 23 2017

Main weather highlights in the long term period are a period of
milder and quieter weather Thursday into Friday, followed by more
cold air for the weekend through Halloween.

Quiet weather day expected for Thursday due to shortwave ridging in
between the exiting upper trough and the next one dropping into the
north central U.S.. Also milder temperatures expected on Thursday
with high temps 55 to 60 as warm advection strengthens in advance of
next approaching system. Friday may also be a mild day if the slower
ECMWF timing of the next cold front is correct.

Deep longwave trough is progged to impact the Great Lakes Region
next weekend, resulting in scattered showers with highs only in the
mid 40s. Some snow showers will be possible at night and in the
early morning when temperatures cool, especially inland from Lake MI
and in higher elevation areas. Any clearing at night could lead to
sub freezing temperatures.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 152 AM EDT Tue Oct 24 2017

Most of the terminals are currently in a break from the widespread
IFR that was in place earlier as it has shifted North and East
with the low. We are expecting lower clouds to move back within
the next few hours as the low deepens and wraps low level moisture
back in. The cigs will likely teeter on the MVFR/IFR threshold
throughout much of the forecast period. These cigs will likely
linger throughout the remainder of the period. Rain showers will
remain around most of the day.

W/SW Winds will pick up this morning, with gusts expected to be
in the 20-30 knots range lasting through the afternoon. The gusts
will likely subside late in the period.

&&

.MARINE...
Issued at 328 PM EDT Mon Oct 23 2017

No significant changes to the previous forecast. Winds and waves
will be increasing tonight and gales are still expected to develop
on Tuesday. Northwest gales will probably begin during the
morning across areas north of Whitehall and during the afternoon
south of there.


&&

.HYDROLOGY...
Issued at 1211 PM EDT Mon Oct 23 2017

River levels are rising across the area. Rainfall of up to two
inches has fallen through this morning and another two to three
inches are possible through Tuesday. More rain is also possible
through the week. Warnings have been issued for Croton on the
Muskegon River, Rockford on the Rogue River, and Vicksburg on the
Portage River. More river warnings could be issued depending on the
amount of rain that falls and where it falls. Areal flood warnings
and watches are also in effect though Tuesday.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Wind Advisory from 2 PM this afternoon to 3 AM EDT Wednesday for
     MIZ050-056-064.

     Wind Advisory from 8 AM this morning to 3 AM EDT Wednesday for
     MIZ037-043.

LM...Small Craft Advisory until 10 AM EDT this morning for LMZ844>849.

     Gale Warning from 10 AM this morning to 8 AM EDT Wednesday for
     LMZ844>849.

&&

$$

UPDATE...MJS
SYNOPSIS...Ostuno
SHORT TERM...Ostuno
LONG TERM...Meade
AVIATION...NJJ
HYDROLOGY...63
MARINE...Ostuno


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